It has previously been suggested to provide a seal around the periphery of a battery, the seal comprising a plurality of layers adhered together and including a metal layer and a hot melt adhesive layer. The hot melt adhesive is activated and the seal is produced by heating the adhesive and other layers in the peripheral area and then letting them cool.
The choice of an adhesive for such purposes is based upon the chemical, physical, and physical-chemical properties which the given adhesive exhibits in its application to a particular seal.
Chemical properties are those such as resistance to the chemical environment of the battery.
The physical properties of an adhesive are customarily measured with bulk property measurements such as tensile strength at rupture, and modulus. The modulus is defined as the stress divided by the strain within the proportional limit (elastic limit) of the stress-strain curve.
The physical-chemical properties which are usually associated with seal materials are measured by means of adhesion measuring techniques to the substrate surfaces involved in the seal.
The selection of the proper adhesive is made difficult due to the presence of the metal layer in the peripheral seal. In addition to being able to withstand higher tensile and shear stresses than the adhesive, the metal also changes dimensions to a much lesser degree than does the adhesive during the cooling step.